The missing Huey, assigned to Marine Light Attack Helicopter Squadron 469, disappeared at about 7 p.m. Tuesday, according to a statement from Joint Task Force 505, which is leading U.S. relief efforts in Nepal following last month’s deadly earthquake.

“At this time, the status of those manifested on the flight is unknown,” the statement said.

The incident came a day after a second large earthquake struck Nepal, a nation already reeling from last month’s temblor, which claimed more than 8,000 lives.

The latest quake, which measured a magnitude of 7.3 and was centered midway between Kathmandu and Mount Everest, struck hardest in the foothills of the Himalayas, triggering landslides, but it also shook the capital badly, sending thousands of terrified people into the streets, according to The Associated Press.

The Marine Huey vanished near Charikot while delivering aid and evacuating casualties to Kathmandu, the JTF 505 statement said.

Nepalese military forces were on the ground in the vicinity of the chopper’s last known location, searching for the missing aircraft Tuesday night, and that had grown into a battalion-sized contingent by Wednesday, the statement said.

Two MV-22B Osprey tilt-rotor aircraft with Marine Medium Tiltrotor Squadron 262 launched from Kathmandu on Wednesday afternoon to take part in the search for the missing Huey, according to a JTF 505 statement.

The 36th Contingency Response Group, also with JTF 505, is continuing to support civil aviation authorities offloading humanitarian aid at Kathmandu’s international airport, a JTF 505 statement said.

U.S. Army Col. Steve Warren, quoted by AP, said an Indian helicopter heard radio chatter from the Marine aircraft about a possible fuel problem. He said the Huey, carrying tarps and rice, had dropped off supplies in one location and was en route to a second when contact was lost. He said officials are hopeful the aircraft is simply missing because there has been no smoke or other signs of a crash.

One of the Marine Huey pilots in Nepal, Capt. Duncan James, 32, of Brady, Texas, said May 3, his first day in-country, that the “Yankee” model helicopters deployed for the relief mission are brand new.

The Marine Corps pilots are used to flying the unpressurised helicopters at 5,000 feet above mountains near their home station — Camp Pendleton, Calif. — but anticipated flying as high as 10,000 feet during the earthquake relief mission, he said.

“It is a little more challenging flying at that altitude, but we have trained to do it,” he said.